Question

我的控制器操作代码如下所示：

  def addIngredient() = Action { implicit request =>
    val boundForm = ingredientForm.bindFromRequest
    boundForm.fold(
      formWithErrors => BadRequest(views.html.Admin.index(formWithErrors)),
      value => {
        Async {
          val created = Service.addIngredient(value.name, value.description)
          created map { ingredient =>
            Redirect(routes.Admin.index()).flashing("success" -> "Ingredient '%s' added".format(ingredient.name))
          }

          // TODO on exception do the following
          // BadRequest(views.html.Admin.index(boundForm.copy(errors = Seq(FormError("", ex.getMessage())))))
        }
      })
  }

我的Service.addIngredient（...）返回Promise [Ingredient]，但也可以抛出自定义的ValidationException。抛出此异常时，我想返回注释代码。

目前页面呈现为500并且在我拥有的日志中：

play - 等待承诺，但收到错误：有名字的成分 'test'已经存在。 services.ValidationException：具有名称的成分 'test'已经存在。

两个问题：

从我的服务中返回此异常是一个坏主意，是否有更好/更多的scala方法来处理这种情况？
如何捕捉异常？

Answer 1

我会说纯粹的功能方式是使用一种可以保存有效和错误状态的类型。

为此，您可以使用Validation表单scalaz

但是如果不需要scalaz（你会^^），你可以使用一个非常简单的东西，使用Promise[Either[String, Ingredient]]作为结果，并在异步块中使用fold方法。也就是说，map转换兑换承诺时的值，并fold转换兑换的内容。

好点=＆gt;没有例外=＆gt;每件事都是打字检查： - ）

修改

它可能需要更多信息，这里有两个选项：try catch，感谢@kheraud）和Either。没有放Validation，如果需要请问我。 object应用程序扩展Controller {

def index = Action { Ok(views.html.index("Your new application is ready.")) } //Using Try Catch // What was missing was the wrapping of the BadRequest into a Promise since the Async // is requiring such result. That's done using Promise.pure def test1 = Async { try { val created = Promise.pure(new {val name:String = "myname"}) created map { stuff => Redirect(routes.Application.index()).flashing("success" -> "Stuff '%s' show".format(stuff.name)) } } catch { case _ => { Promise.pure(Redirect(routes.Application.index()).flashing("error" -> "an error occurred man")) } } } //Using Either (kind of Validation) // on the Left side => a success value with a name val success = Left(new {val name:String = "myname"}) // on the Right side the exception message (could be an Exception instance however => to keep the stack) val fail = Right("Bang bang!") // How to use that // I simulate your service using Promise.pure that wraps the Either result // so the return type of service should be Promise[Either[{val name:String}, String]] in this exemple // Then while mapping (that is create a Promise around the convert content), we folds to create the right Result (Redirect in this case). // the good point => completely compiled time checked ! and no wrapping with pure for the error case. def test2(trySuccess:Boolean) = Async { val created = Promise.pure(if (trySuccess) success else fail) created map { stuff /* the either */ => stuff.fold( /*success case*/s => Redirect(routes.Application.index()).flashing("success" -> "Stuff '%s' show".format(s.name)), /*the error case*/f => Redirect(routes.Application.index()).flashing("error" -> f) ) } } }

Answer 2

你不能只在异步块中捕获异常吗？

Async {
    try {
        val created = Service.addIngredient(value.name, value.description)
        created map { ingredient =>
            Redirect(routes.Admin.index()).flashing("success" -> "Ingredient '%s' added".format(ingredient.name))
        }
     } catch {
         case _ => {
             Promise.pure(Redirect(routes.Admin.index()).flashing("error" -> "Error while addin ingrdient"))
         }
     }
}

如何处理playframework中的异常2异步块（scala）

2 个答案: